| 1. |
- Adebahr, Josefina, et al.
(författare)
-
Cation coordination in ion-conducting gels based on PEO-grafted polymers
- 2000
-
Ingår i: Solid State Ionics. - 0167-2738. ; 135:1-4, s. 149-154
-
Tidskriftsartikel (refereegranskat)abstract
- Ionic conducting polymer gels prepared from PEG-grafted acrylates, ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 are studied by means of infrared and Raman spectroscopy. It is found that the presence of grafted PEO chains substantially changes the coordination of lithium cations from 'cation-solvent' to 'cation-polymer'. Spectroscopic studies show that Li+-PEO coordination is strongly favored in competition with the solvent molecules and dominates completely at ether oxygen to Li-cation ratios (O:Li) of 10:1 and 5:1. At an O:M of 4:1 a solvent-cation interaction arises, in agreement with previously reported MD calculations of a preferred coordination number of 5 in similar systems. The results suggest that the complex interactions which determine long time stability and ionic transport properties can be designed by functionalization of the polymer backbone in PMMA-based gel electrolytes.
|
|
| 2. |
- Andersson, Ove, et al.
(författare)
-
A high-pressure study of PMMA-based gels with and without TiO2 nano-particle filler: a filler induced change in the activation volume
- 2005
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 50:16-17, s. 3217-3223
-
Tidskriftsartikel (refereegranskat)abstract
- The ionic conductivity σ of PMMA-based gels with and without nano-particle filler has been investigated at elevated pressure up to 0.9 GPa and in the temperature range 220-330 K to determine the effect of pressure and to obtain the activation volume. Both gels had molar ratios: EC:PC:LiClO 4 :PMMA 53.9:22:5.2:18.9, and one gel contained 8 wt.% TiO 2 nano-particles. At room temperature and atmospheric pressure, the conductivity of the gel with filler is almost the same as that for the gel without filler. At increasing pressure p, σ(p) for both gels exhibits an abrupt change, which is associated with a transition, and consequently there is a pressure induced change in the activation volume for both gels. The activation volume ΔV * in low-pressure state is the same for the gels with and without filler and about 14 cm 3 mol -1 at room temperature, which is typical liquid-like behaviour. In the high-pressure state, ΔV * = 42 and 45.3 cm 3 mol -1 at 294 K for the gels with and without filler, respectively. The results show that the ionic movements are restricted by the rigid environment of the high-pressure state and that the filler affects ΔV * under this condition. In particular, the filler appears to improve the cation transport number as a results of a decreased mobility of large-sized ions in the rigid environment of the high-pressure state. © 2004 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Bermudez, V. D., et al.
(författare)
-
Eu3+ coordination in an organic/inorganic hybrid matrix with methyl end-capped short polyether chains
- 2005
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 109:15, s. 7110-7119
-
Tidskriftsartikel (refereegranskat)abstract
- Fourier Transform mid-infrared (FT-IR), Fourier Transform Raman (FT-Raman) and photoluminescence spectroscopies and Two-Dimensional (2D) Correlation Spectroscopic Analysis were employed to examine the anionic and cationic local environments in mono-urethanesils doped with europium triflate (Eu(CF 3-SO3)3). The hybrid host framework of these materials is composed of a siliceous backbone bonded through urethane linkages to CH3-terminated polymer chains containing about 7 OCH 2CH2 units. Samples with ∞ ≥ n (composition) ≥5 (where n = OCH2CH2/Eu3+) were studied. In terms of ionic association, the level of complexity of these xerogels is very high. In all the compounds the triflate ions exist "free", weakly coordinated and forming cross-link separated ion pairs. At 20 ≥ n ≥ 5, in addition to all these species contact ion pairs occur. In agreement with these conclusions, photoluminescence establishes the presence of three distinct cation local sites (Eu3+/O=C(urethane cross-links), Eu3+/O-C- C(polyether chains) and weakly coordinated Eu3+/CF3SO 3- ionic pairs).
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Carlos, L. D., et al.
(författare)
-
Nanoscopic photoluminescence memory as a fingerprint of complexity in self-assembled alkyl/siloxane hybrids
- 2007
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 19:3, s. 341-348
-
Tidskriftsartikel (refereegranskat)abstract
- A thermally activated photoluminescence memory effect, induced by a reversible order-disorder phase transition of the alkyl chains, is reported for highly organized bilayer alkyl/siloxane hybrids (see figure; left at room temperature, right at 120 degrees C). The emission energy is sensitive to the annihilation/formation of the hydrogen-bonded amide-amide array displaying a unique nanoscopic sensitivity (ca. 150 nm).
|
|
| 7. |
- Goncalves, M. C., et al.
(författare)
-
Local structure and near-infrared emission features of neodymium-based amine functionalized organic/inorganic hybrids
- 2005
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 109:43, s. 20093-20104
-
Tidskriftsartikel (refereegranskat)abstract
- Nd3+-based organic/inorganic hybrids have potential application in the field of integrated optics. Attractive sol-gel derived di-urea and di-urethane cross-linked poly (oxyethylene) (POE)/siloxane hybrids (di-ureasils and di-urethanesils, respectively) doped with neodymium triflate (Nd(CF3SO3)(3)) were examined by Fourier transform mid-infrared (FT-IR), Raman (FT-Raman), Si-29 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and photoluminescence spectroscopies, and small-angle X-ray scattering (SAXS). The goals of this work were to determine which cation coordinating site of the host matrix (ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the photoluminescence properties. The main conclusion derived from this study is that the hydrogen-bonded associations formed throughout the materials play a major role in the hybrids nanostructure and photoluminescence properties.
|
|
| 8. |
- Gonçalves, Maria M., et al.
(författare)
-
Cationic and anionic environments in mono-urethanesil hybrids doped with magnesium triflate
- 2004
-
Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 166:1-2, s. 103-114
-
Tidskriftsartikel (refereegranskat)abstract
- Sol–gel derived poly(oxyethylene), POE/siloxane hybrids (mono-urethanesils) with a wide range of magnesium triflate (Mg(CF3SO3)2) concentrations were analyzed by infrared and Raman spectroscopies with the goal of examining the cation/polymer, cation/cross-link, hydrogen bonding and cation/anion interactions. In the host matrix of these xerogels short CH3-terminated POE segments are covalently bonded to the siliceous backbone through urethane linkages. Samples with ∞>n≥6 (where n is the molar ratio of (OCH2CH2) moieties per Mg2+ ion) were synthesized.The spectral data obtained provided conclusive evidence that the ether oxygen atoms of the polymer chains of the host structure complex the alkaline-earth ions in materials with n≤60. "Free" triflate ions and weakly coordinated anions were detected over the whole range of salt concentration examined. The coordinated triflate species are formed in two different bonding environments. Contact ion pairs appear in materials with n≤60.This work confirms previous studies that suggested that the nature of the cations added to the mono-urethanesil-type framework plays a key-role in the properties of these composites.
|
|
| 9. |
- Londero, Elisa, 1982, et al.
(författare)
-
Desorption of n-alkanes from graphene: a van der Waals density functional study
- 2012
-
Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42, s. 424212-
-
Tidskriftsartikel (refereegranskat)abstract
- A recent study of temperature-programmed desorption (TPD) measurements of small linear alkane molecules (n-alkanes, with formula CNH2N+2) from C(0001) deposited on Pt(111) shows a linear relationship of the desorption energy with increasing n-alkane chain length N. We here present a van der Waals density functional study of the desorption barrier energy of the ten smallest n-alkanes (of carbon chain length N = 1–10) from graphene. We find linear scaling with N, including a non-zero intercept with the energy axis, i.e. an offset at the extrapolation to N = 0. This calculated offset is quantitatively similar to the results of the TPD measurements. From further calculations of the polyethylene polymer we offer a suggestion for the origin of the offset.
|
|
| 10. |
- Nunes, S. C., et al.
(författare)
-
Cation coordination and hydrogen bonding in potassium and magnesium based-di-amidosil hybrids
- 2008
-
Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860. ; 874:1-3, s. 128-137
-
Tidskriftsartikel (refereegranskat)abstract
- Fourier transform mid-infrared and Raman spectroscopies were employed to elucidate the cation/alkylene chains, cation/cross-link, cation/anion interactions and hydrogen bonding occurring in amorphous di-amide cross-linked alkylene/siloxane hybrid materials (diamidosils) doped with potassium and magnesium triflates (KCF3SO3 and Mg(CF3SO3)(2), respectively). Materials with compositions infinity > n >= 5 (where it expresses the molar ratio of carbonyl oxygen atoms per guest cation) were investigated. The conformations (gauche) of the alkylene chains of the host di-amidosil matrix are not affected by the presence of the guest salt in both doped di-amidosil families. The K+ and M2+ ions coordinate to the carbonyl oxygen atoms of the amide cross-links within the whole range of salt concentration considered, leading to the saturation of the cross-linkages, to a redistribution of the amide-amide hydrogen-bonded aggregates of the host matrix and, in the case of the K+-doped sample with n = 10, to the formation of a new type of aggregate, stronger and more ordered than those detected at lower salt content. In both di-amidosil systems guest salt addition leads to the increase of ionic associated species and to a concomitant decrease of the concentration of "free" anions. (c) 2007 Elsevier B.V. All rights reserved.
|
|
